Lin DeVecchio was a highly decorated FBI agent who helped put some of the mafia's most notorious leaders behind bars. He's also one of the few FBI agents ever charged with murder. It was his relationship with a violent mob informant known as "The Grim Reaper" that got him and the FBI in trouble.
He's now telling the story for the first time in a new book and on "60 Minutes." It's rare to get an inside look at the shadowy world of informants and their handlers; it's rarer still to hear an FBI agent describe a brutal mafia killer as his friend. But that is exactly what Lin DeVecchio told us.
He says his informant's information helped cripple the mob. To get it, however, DeVecchio has been accused of making a deal with the devil.
"I didn't make any bargains with the devil," DeVecchio told CNN's Anderson Cooper. "I wasn't dancing with the devil. I was dancing with a guy that was very close to the devil, he was a tough guy. But that was what they were paying me to do. I got close to members of organized crime so we can eliminate them."
Asked if he felt like he walked up to the line, DeVecchio said, "Yeah, sure, I got close to it. I freely admit that."
In the 1980s, the mafia was a big problem in New York City. Surveillance footage was as close as law enforcement often got -- including scenes shot outside a mob hangout called the "Wimpy Boys Social Club" in Bensonhurst, Brooklyn, an area then controlled by the Colombo family.
One of the most notorious wise guys was Greg Scarpa, who had a reputation for brutality.
DeVecchio says Scarpa was "was absolutely fearless. One of the toughest guys I've ever seen."
His toughness may have been legendary but what no one in the Colombo family knew was that Greg ("The Grim Reaper") Scarpa was also a rat. In the 1960s, he had secretly provided the FBI with detailed information about fellow mobsters but he'd had a falling out with the bureau and broke off relations.
In 1980, DeVecchio wanted Scarpa back, so he decided to take a big chance: he drove up to the gangster's home unannounced and blocked Scarpa's car as he was pulling out of his driveway.
"He was like, 'Who the f--- are you?'" DeVecchio remembered. "And I said, 'You know, I'd like to speak with you. I do need some help. You know, I want to get schooled in the life. You know, educate me.' About two weeks later he called. And he said, 'Come alone.' And I did."
FBI agents aren't supposed to meet alone with informants, but DeVecchio got special permission. Scarpa was considered a top echelon informant, and great care was taken to keep their meetings secret.
When law enforcement officials announced one of the most important prosecutions ever against the mob in 1985, very few people knew that Scarpa's information had played a role. It was called the "Commission Case," and it not only catapulted a young prosecutor named Rudy Giuliani into the limelight, but also sent the heads of three of the five crime families away for life.
DeVecchio got promoted and ended up leading two organized crime squads in New York; Scarpa got paid $66,000 for the information he supplied over 12 years, and when he was arrested for credit card fraud, DeVecchio helped keep him out of jail.
"His career and his life and his milieu that he worked in was so different than mine, that it was fascinating to me to learn about that," DeVecchio said. "I liked the guy. You know, I make no bones about that. I'm not ashamed of that. Doesn't mean I condone what he did."
Asked if it was a friendship, DeVecchio acknowledged, "It was a friendship. Absolutely."
Produced by Andy Court and Anya Bourg